Shear seal blowout preventer

Abstract

A shear/seal ram provides a knife edge at the shearing edge and the knife edge is inclined to minimize the cutting force required and to leave a clean cut edge. The knife edge is presented in an opening of the ram, thus the opening is positioned at the axis of the BOP, and consequently the coiled tubing, before the coiled tubing is run through the BOP. A biasing means, such as for example a Bellville spring, forces a sealing sleeve against the underside of the ram to prevent leakage of pressure from below the BOP. Similarly, a plurality of biasing means, referred to herein as “skates”, forces the ram down against the sealing sleeve to seal pressure from above the BOP.

I claim: 
     
       1. A blowout preventer for severing a tubular, the tubular positionable in a wellbore penetrating a subterranean formation, comprising:
 a body having an axial bore and a radial bore therethrough, the tubular positionable through the axial bore, the body having a tube receiving cavity extending radially about a portion of the axial bore and defining a pocket between the axial bore and the radial bore to receive a portion of the tubular upon severing, the pocket extending about a portion of a horizontal circumference of the axial bore; and 
 a ram having a ram bore therethrough, the ram slidably positionable in the radial bore between a refracted position and an extended position, the tubular positionable through the ram bore and the axial bore when the ram bore is in the retracted position; and 
 a knife positionable about the ram bore to sever the tubular as the ram moves from the retracted to the extended position, a severed end of the tubular receivable in the tube receiving cavity as the tubular is severed. 
 
     
     
       2. The blowout preventer of  claim 1 , wherein the tube receiving cavity extends about less than a periphery of the axial bore. 
     
     
       3. The blowout preventer of  claim 1 , further comprising a ram-receiving chamber operatively connectable to the body, the ram slidably positionable in the ram receiving chamber. 
     
     
       4. The blowout preventer of  claim 1 , further comprising a bonnet operatively connected to the body, the ram receivable by the bonnet. 
     
     
       5. The blowout preventer of  claim 1 , further comprising a ram-receiving chamber operatively connectable to the body, the ram slidably positionable in the ram receiving chamber and a bonnet operatively connected to the body, the ram receivable by the bonnet, the bonnet is positioned about the body on a side opposite from the ram receiving chamber. 
     
     
       6. The blowout preventer of  claim 5 , further comprising a cylinder with a piston slidably positionable in the bonnet, the ram operatively connected to the piston. 
     
     
       7. The blowout preventer of  claim 1 , wherein the ram bore has one of a circular and a tear-drop shape. 
     
     
       8. The blowout preventer of  claim 1 , further comprising an upstream seal positionable in the body about the axial bore and upstream of the radial bore. 
     
     
       9. The blowout preventer of  claim 1 , further comprising a seal positionable in the body about the axial bore and downstream of the radial bore. 
     
     
       10. The blowout preventer of  claim 1 , further comprising a spring and a seal positionable in the body about the axial bore, the spring supporting the seal in the body. 
     
     
       11. The blowout preventer of  claim 1 , wherein the knife comprises a tapered surface along a portion of an inner periphery of the ram bore. 
     
     
       12. The blowout preventer of  claim 1 , wherein the knife has an angled surface positionable along a portion of an inner periphery of the ram bore. 
     
     
       13. The blowout preventer of  claim 1 , wherein the ram has an angled surface along a portion of an inner periphery of the ram bore, the inner periphery shaped to push the severed end of the tubular into the tube receiving cavity. 
     
     
       14. The blowout preventer of  claim 1 , further comprising a skate operatively connected to the ram. 
     
     
       15. A system for severing a tubular, the tubular positionable in a wellbore penetrating a subterranean formation, comprising:
 a blowout preventer, comprising:
 a body having an axial bore and a radial bore therethrough, the tubular positionable through the axial bore, the body having a tube receiving cavity extending radially about a portion of the axial bore and defining a pocket between the axial bore and the radial bore to receive a portion of the tubular upon severing, the pocket extending about a portion of a horizontal circumference of the axial bore; and 
 a ram having a ram bore therethrough, the ram slidably positionable in the radial bore between a retracted position and an extended position, the tubular positionable through the ram bore and the axial bore when the ram bore is in the retracted position; and 
 a knife positionable about the ram bore to sever the tubular as the ram moves from the retracted to the extended position, a severed end of the tubular receivable in the tube receiving cavity as the tubular is severed; 
 
 a seal positionable in the body adjacent the ram by a spring; and 
 a depressor to compress the at least one seal into the body. 
 
     
     
       16. The system of  claim 15 , wherein the tube receiving cavity extends about less than a periphery of the axial bore. 
     
     
       17. The system of  claim 15 , wherein the ram has an angled surface along a portion of an inner periphery of the ram bore, the inner periphery shaped to push the severed end of the tubular into the tube receiving cavity. 
     
     
       18. A method for severing a tubular, the tubular positionable in a wellbore penetrating a subterranean formation, comprising:
 positioning a blowout preventer about the tubular, the blowout preventer comprising:
 a body having an axial bore and a radial bore therethrough, a ram having a ram bore therethrough, and a knife positionable about the ram bore, the body having a tube receiving cavity extending radially about a portion of the axial bore and defining a pocket between the axial bore and the radial bore, the pocket extending about a portion of a horizontal circumference of the axial bore; 
 
 severing the tubular by engaging the tubular with the knife while slidably moving the ram in the radial bore from a retracted position with the tubular positioned through the radial bore and the axial bore and an extended position a distance therefrom; and 
 receiving a severed end of the tubular in the tube receiving cavity. 
 
     
     
       19. The method of  claim 18 , further comprising pushing the severed end of the tubular into the tube receiving cavity with the ram during the severing. 
     
     
       20. The method of  claim 18 , further comprising pushing the severed end of the tubular into the tube receiving cavity with a slanted portion of an inner periphery of the ram bore during the severing.